1. Field of the Invention
This invention relates to an apparatus, method and system for defining a pattern on a substrate and more particularly relates to an apparatus, method and system for fabricating servo patterns on high density patterned media.
2. Description of the Related Art
Hard-disk drives provide data storage for data processing systems in computers and servers, and are becoming increasingly pervasive in media players, digital recorders, and other personal devices. Advances in hard-disk drive technology have made it possible for a user to store an immense amount of digital information on an increasingly small disk, and to selectively retrieve and alter portions of such information almost instantaneously. Particularly, recent developments have simplified hard-disk drive manufacture while yielding increased track densities, thus promoting increased data storage capabilities at reduced costs.
In a hard-disk drive, rotating high precision aluminum or glass disks are coated on both sides with a special thin film media designed to store information in the form of magnetic patterns. Electromagnetic read/write heads suspended or floating only fractions of micro inches above the disk are used to either record information onto the thin film media, or read information from it.
A read/write head may write information to the disk by creating an electromagnetic field to orient a cluster of magnetic grains, known as a bit, in one direction or the other. To read information, magnetic patterns detected by the read/write head are converted into a series of pulses which are sent to the logic circuits to be converted to binary data and processed by the rest of the system. To increase the capacity of disk drives, manufacturers are continually striving to reduce the size of bits and the grains that comprise the bits.
The ability of individual magnetic grains to be magnetized in one direction or the other, however, poses problems where grains are extremely small. The superparamagnetic effect results when the product of a grain's volume (V) and its anisotropy energy (Ku) fall below a certain value such that the magnetization of that grain may flip spontaneously due to thermal excitations. Where this occurs, data stored on the disk is corrupted. Thus, while it is desirable to make smaller grains to support higher density recording with less noise, grain miniaturization is inherently limited by the superparamagnetic effect.
In response to this problem, engineers have developed patterned media, where the magnetic thin film layer is created as an ordered array of highly uniform islands, each island capable of storing an individual bit. Each bit may be one grain, or several exchange coupled grains, rather than a collection of random decoupled grains. In this manner, patterned media effectively reduces noise by imposing sharp magnetic transitions at well-defined pre-patterned positions, known as bit patterns. Bit patterns are organized as concentric data tracks around a disk.
A head-positioning servomechanism facilitates the ability of a read/write head to locate a particular data track location and to reposition the head from one location to another. Indexing marks and alignment indices maybe recorded in arc-shaped regions of the disk surface, known as servo sectors, and referenced by the servomechanism to maintain proper dynamic positioning capabilities of the read/write head over time. Track addresses, synchronization signals, and position error signal (“PES”) bursts may also be recorded in servo sectors.
While recent developments in hard-disk drive manufacture have facilitated generation of patterned media having increased track densities, servo pattern fabrication considerations have been largely ignored. Servo patterns must therefore be fabricated in a separate process that is generally time-consuming, labor-intensive, and costly.
The recently developed shadow mask approach to hard disk-drive manufacture, for example, is used to increase the density of data islands beyond the capability of e-beam lithography. This approach creates multiple features for each feature on the shadow mask, where each feature on the substrate has a predetermined position offset relative to the corresponding shadow mask feature. Despite the data island production efficiencies accomplished with the shadow mask approach, however, the shadow mask inherently constrains the nature of patterns that can be created on the substrate. Servo patterns thus have been generated using a separate process that is time-consuming, labor-intensive and costly.
Accordingly, a need exists for a practical, attainable apparatus, system, and method for utilizing a shadow mask to form servo patterns on high density patterned media. Beneficially, such an apparatus, system and method would cooperate with the shadow mask approach to track or bit pattern fabrication to produce servo patterns and a high density track or bit pattern substantially simultaneously to reduce costs, labor and resources traditionally associated with patterned media fabrication. Such apparatuses, systems and methods are disclosed and claimed herein.